(1) Field of the Invention
The present invention relates to an improved packaging machine for use in packaging a constant amount of a charge continuously in containers made from tubularly shaped plastic film.
(2) Description of the Prior Art
A conventional packaging machine for filling containers made from tubularly shaped plastic film, and its operating procedure will be described with reference to FIGS. 3A-3D.
Generally, tubular film 1, packed with a charge 2, is heat-sealed by members 4 at a predetermined sealing position, such as shown at 6 in FIG. 3A. To the film beneath the sealing position 6 is attached a packaged container 1a which has been previously formed. The tubular plastic film above the sealing position 6 is supplied with a filling charge 2 in a predeterminedly constant amount. A pair of squeezing rolls 3 is arranged above the heat-sealing members 4 and is located at such a position as to permit the forming of a packaged container. As shown in FIG. 3B, the squeezing rolls 3 are moved toward each other to press and divide the tubular film 1 filled with the charge 2 into a length required by one packaged container 1b. Subsequently, the squeezing rolls 3 are rotated in the direction of the arrows (FIG. 3C) to push the filled container 1b downward under the heat-sealing members. These members are then in the position shown by phantom lines and move in the direction indicated by the arrows (FIG. 3C), sealing the film above the filled container. A pair of cutting members 5 is arranged on opposite sides of the downwardly moved, sealed portion 6 (bottom or leading end of the packaged container) and the cutting members are moved toward each other to sever the previously sealed and formed container at the sealing position 6. Thereafter, the squeezing rolls 3 and the heat-sealing members 4 are, respectively, separated from each other and the charge 2 is supplied into the tubular film 1, the packaging operation being performed continuously in the same sequential manner.
Drawbacks and problems, unfortunately, arise in the use of the packaging machine described above. For example, when handling a hot charge, the sealed portion 6 may be readily torn apart due to insufficient cooling when the hot charge flows into the film (steps of FIGS. 3A and 3D), causing a loss of the charge and of the film. Further, although (see FIG. 3C) the distance L;hd 2 between the squeezing rolls 3 and the sealing members 4 and the distance L.sub.1 between the sealing members 4 and the cutting members 5 are arranged so as to permit cutting of the film at the sealed portion 6, the cutting could occur in an undesirable position, thereby causing the loss of the charge and of the film and the contamination of the environment of the machine. This would lead to a reduced working efficiency, because in actual operation the length of a packaged container 1a, 1b is not necessarily constant, due to e.g. variations in the conditions of the charge's temperature, etc.